RATE-DEPENDENT HEMODYNAMIC-RESPONSES DURING INCREMENTAL ATRIAL-PACINGIN CHRONIC CONSTRICTIVE PERICARDITIS BEFORE AND AFTER SURGERY

Chronic constrictive pericarditis is a frequent cause of diastolic dys function, and results in impaired ventricular filling. Unlike in norma l subjects, ventricular filling in constrictive pericarditis occurs al most entirely in the initial one third of diastole, and cardiac output is dependent predominantly on heart rate. Tachycardia impairs ventric ular filling in normal subjects, but its effects in patients with cons trictive pericarditis have not been studied. The effect of increasing heart rate alone with atrial pacing on the central and peripheral hemo dynamics of patients with untreated chronic constrictive pericarditis before and after pericardiectomy was evaluated. Increased heart rate w ith atrial pacing increased cardiac output, whereas stroke volume rema ined unchanged up to heart rates of 140 beats/min. Further increases i n heart rate resulted in reductions of cardiac output and stroke volum e. Them were no significant changes in ventricular filling pressures. Infusion of 300 ml of saline solution at peak pacing rates did not imp rove cardiac output. After successful surgical pericardiectomy, the he modynamic effects of atrial pacing returned to normal. It is concluded that moderate tachycardia improves the hemodynamic profile of patient s with constrictive pericarditis.